The effect of varying levels of readily available carbohydrates on urea utilization PublicDeposited

Descriptions

The object of this research was to study the effect of readily
available carbohydrates (RAC) upon the utilization of urea in fattening
rations and to determine the effect upon carcass characteristics
that determine quality and yield grades. A 2 x 2 latin square designed
feedlot trial comparing urea at 0.5% and 1.5% and molasses
at 2.5% and 7.5% of the ration resulted in a significant interaction
(p < .01) for rumen ammonia, acetic, valeric, and isovaleric acids,
total VFA, and butyric acid (p < .05) concentrations. Urea and molasses
additions significantly (p < .01) increased acetic and propionic
acid levels but molasses decreased (p < .05) the molar % of acetic
acid.
Carcass characteristics were not affected by the urea or molasses
treatments. Individual VFA concentrations had a low correlation
to carcass characteristics, accounting for less than 20% of the total
variability.
In a standard metabolism trial comparing fattening rations
containing 0% or 1.5% urea and varying levels of RAC from 42% to
53%, the apparent digestibility of the feed components was not
significantly (p > .1) affected by substituting 1.5% urea for natural
protein. The percent of absorbed N retained increased 0.90% for
each 1% increase in RAC, yielding a regression equation, y =
64.98 + 0.8134 (X-47). The percent N retained increased 0.82%
for each 1% increase in RAC and can be expressed by the regression
equation, Y = 46.82 + . 7471 (X-47). This would suggest as the RAC
level of the ration increased urea is more efficiently incorporated
into protein.